The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

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awemawson:
This afternoon I reverted to my original SMCC card (the servo subsystem card that drives the turret via Siemens power amplifiers)

Initially the turret would unlock by driving the tool disk forwards, but when rotated wouldn't re-lock when driven back due to angular error. Driving it to the correct position by manipulating the lock / unlock solenoids and physically turning it, it then would settle back and I was able to select tools by program.

I get the impression that the positioning is not spot on as the re-coupling of the curvic coupling is a bit hesitant. I came to the conclusion then that the output stage of the SMCC controller had a small error offset due to a hardware issue.

OK this where I was a couple of years back before shingles destroyed my brain. I have sourced another SMCC card that was in another Beaver TC20 lathe but that one was controlled by a Fanuc PLC. Reading it's internal program it is virtually the same as my one only differing in a couple of lines but these are to do with addressing the card so probably crucial.

My attempts at programming these cards in the past have drawn a blank - more research needed.

tom osselton:
It’s coming along nicely

awemawson:
Well it WAS Tom but now I'm in the 'one step forwards, three back' scenario !

So with the progress shown in my last post I left it for the evening and returned the next day to find the servo system totally refused to function with the PLC reporting "6022 Axis Drive Fault". Now the Axis Drive Fault is reported to line 404 of socket X121 on the 'Measuring Card' and is derived from the Siemens Servo drive box control card 6SC6100-06B00 in the servo crate. It just so happens that I have a known good spare so I swapped it. No change in the symptoms.

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Maybe it's the "Measuring Card" in the 820T? This card drives the axis servos, has all the various encoder interfaces and is buried deep in the 820T Siemens Control - access to change cards is possible but by no mean straight forwards due to physical constraints. I changed it. OH heck now nothing on the monitor screen - replaced original card - still nothing - argh !!!!

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At this stage with nothing to loose I have pulled the entire Siemens 820T control from it's rack for bench diagnosis and am retiring to lick my wounds. Looking far back in this saga I've confirmed that I could power it up and get data on the monitor with nothing else in the way of interfaces connected so my next approach will at least physically far easier!

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awemawson:
So having enjoyed a smoked mackerel salad with home grown tomatoes for lunch (very nice ) I threw caution to the winds and connected up a local mains supply so that I could continue diagnosis.

Much to my surprise the monitor came to life showing what it should (don't worry about the low battery warning - it's disconnected at the moment.

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So now I suppose it's a case of tapping and wriggling to see what had come loose - assuming some sort of mechanical issue.

. . . . the plot thickens :scratch:

vtsteam:
Andrew, some days problems are strictly additive. I think it's the moon phase or something. :coffee: :beer:

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